• ISSN 1008-505X
  • CN 11-3996/S

水氮耦合对滴灌棉田土壤有机碳组分及酶活性的影响

Effects of coupled water and nitrogen on soil organic carbon fractions and enzymes in a drip-irrigated cotton field

  • 摘要:
    目的 研究灌水量和施氮量对滴灌棉田土壤有机碳、氮含量及有机碳库稳定性的影响,为实现新疆棉花高效生产和可持续发展提供理论依据。
    方法 采用两因素三水平完全随机区组设计进行棉花田间滴灌施肥试验,设置的3个灌水量(W)分别为360 mm (低量)、480 mm (适量)、600 mm (高量) ,3个施氮(N)水平分别为0 kg/hm2、300 kg/hm2 (适量)和450 kg/hm2 (高量),共9个处理组合。棉花收获后,采集0—20 cm土层土壤,测定土壤有机碳(SOC)、水溶性有机碳(WSOC)、微生物生物量碳(MBC)、易氧化有机碳(EOC)和稳定态有机碳(NOC)含量,测定土壤脲酶(URE)、β-葡萄糖苷酶(BG)、N-乙酰基-β-D葡萄糖苷酶(NAG)活性利用田间原位填埋尼龙网袋法测定各处理土壤有机物料(秸秆)分解率(OMDR),计算土壤碳库管理指数(CPMI)。
    结果 与W600N450处理相比,2015和2016年W480N300处理土壤有机碳分别提高了8.9%和10.9%,C/N分别提高了16.2%和16.3%,EOC和NOC含量分别提高了11.8%~15.4%和14.3%~20.8%,WSOC含量分别降低了35.5%和21.8%。表明合理的水氮管理有利于提高土壤有机碳和稳定态有机碳含量,降低水溶性有机碳含量,提高土壤碳库的稳定性。与W480处理相比,W360处理MBC含量显著降低了13.1%,W600处理降低了WSOC和NOC含量;W360处理EOC含量两年分别降低了2.1%和5.3%,W600处理分别降低了4.1%和7.6% (P<0.05)。与N300处理相比,N0处理MBC含量降低了41.8%,N450处理降低了NOC含量,N0处理两年EOC含量分别降低了20.2%和16.7%,N450处理分别降低了3.8%和2.4%。表明施氮量对土壤有机碳组分含量的影响大于灌水量。同时,过量的灌水和施氮会降低稳定态有机碳含量,提高微生物生物量碳含量,不利于土壤有机碳的积累。高水(600 mm)和高氮(450 kg/hm2)显著提高了土壤酶活性,降低了土壤碳库管理指数。W480N300处理脲酶、β-葡萄糖苷酶和N-乙酰基-β-D-葡萄糖苷酶活性较W360N0分别提高了1.0%、22.4%和32.6%。W480N300处理下土壤CPMI最高。相关性分析结果表明,CPMI与活性有机碳(MBC、EOC)含量之间存在不同程度的正相关关系,与NOC含量存在负相关关系。
    结论 在新疆滴灌施肥条件下,过高的灌水量和施氮量会降低土壤有机碳和稳定态有机碳含量,降低土壤碳库活度和碳库管理指数,提高微生物生物量碳含量以及酶活性,不利于维持土壤有机碳的稳定。本试验条件下,灌水480 mm配合施氮300 kg/hm2的水氮管理有利于促进滴灌棉田土壤有机碳积累,提高有机碳活性。

     

    Abstract:
    Objective The effects of irrigation and nitrogen application on soil organic carbon, nitrogen content, and organic carbon pool stability in drip-irrigated cotton fields were studied to provide a theoretical basis for achieving efficient cotton production and sustainable development in Xinjiang.
    Methods A two-factor three-level complete random field experiment was conducted using cotton as the test material. The three irrigation volumes (W) were low (360 mm), medium (480 mm), and high (600 mm), and the three nitrogen rates (N) were low (0 kg/hm2), medium (300 kg/hm2), and high (450 kg/hm2), giving a total of 9 treatment combinations. After harvesting the cotton, we collected 0– 20 cm soil samples to measure soil organic carbon (SOC), water soluble organic carbon (WSOC), microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), stable organic carbon (NOC), soil urease (URE), β- Glucosidase (BG), and N-acetyl-β-D-glucosidase (NAG) activity. The soil organic matter decomposition rate and soil carbon pool management index (CPMI) were measured using the net nylon bag method at the in-situ landfill on the field.
    Results SCompared with W600N450, W480N300 increased soil organic carbon by 8.9% and 10.9%, C/N by 16.2% and 16.3%, EOC and NOC by 11.8%–15.4% and 14.3%–20.8%, while WSOC decreased by 35.5% and 21.8% in 2015 and 2016, respectively. It was shown that reasonable water and nitrogen management was beneficial to increasing soil organic carbon and stable organic carbon content, reducing water-soluble organic carbon, and improving soil carbon pool stability. Compared with W480, W360 (P<0.05) reduced MBC, while W600 reduced WSOC and NOC. The EOC content in W360 (P<0.05) decreased by 2.1% and 5.3% in two years, while that in W600 decreased by 4.1% and 7.6%, respectively. Compared with N300, the N0 treatment reduced MBC by 41.8%, while N450 reduced NOC. The EOC in the N0 treatment decreased by 20.2% and 16.7% in two years, while that in N450 decreased by 3.8% and 2.4%, respectively. The results showed that the effect of nitrogen application rate on soil organic carbon was greater than the irrigation level. Simultaneously, excessive irrigation and nitrogen application reduced stable organic carbon and increased microbial biomass carbon, which was not conducive to soil organic carbon accumulation. High irrigation (600 mm) and nitrogen (450 kg/hm2) (P<0.05) increased soil enzyme activity and decreased soil carbon management index. The activities of urease, β-glucosidase, and N-acetyl-β-D-glucosidase in W480N300 were 1.0%, 22.4%, and 32.6% higher than in W360N0. The correlation analysis showed that CPMI was positively correlate with active organic carbon (MBC, EOC) in different degrees and negatively correlate with NOC.
    Conclusion Under drip irrigation conditions in Xinjiang, excessive irrigation and nitrogen application rates reduce soil organic carbon, stable organic carbon, soil carbon pool activity, and carbon pool management index. In contrast, they increase microbial biomass carbon and enzyme activity, which is not conducive to maintaining soil organic carbon stability. In this study, 480 mm irrigation combined with 300 kg/hm2 nitrogen application rate is conducive to promoting soil organic carbon accumulation and improving soil organic carbon activity in drip-irrigated cotton fields.

     

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